Boqueria Chef Marc Vidal on This Weekend's Calçotada Festival

Marc Vidal, chef of the growing Boqueria empire that launched in Flatiron in 2006, takes hold of a green shoot, pinches the bottom of the attached white bulb and, as if peeling off long underwear after a cold winter day, slips off the charred skin of what looks like a green onion. He holds up the naked white remains for a second before he dips them in a rust-hued sauce, tips his head back, and lets the vegetable ribbon into his mouth.

This, he explains, is the traditional way to eat the calçot, a sweet onion so revered in Catalonia it has inspired festivals and restaurants dedicated to it -- and will be a centerpiece at the Calçotada celebration Boqueria is holding on Memorial Day.

"The calçot festival started like 100 years ago," says Vidal. "In Valles, a city 60 miles south of Barcelona, this guy started taking the sprout of an onion when it was super tender and young and grilling it. It became a tradition in the city and a Catalan gastronomic festivity."

Calçots are now cultivated for sweetness, and farmers pack each plant with dirt as it grows to protect the fragile white part from the sun. Once harvested, cooks wrap the onions before placing them on the grill under red roof tile and cooking them until the skin is blistered and charred. The calçots are then served--the roof tiles still on top of the packet--with a side of romesco, a pasty, tangy blend that varies a bit by town but often mixes roasted tomatoes, garlic, sherry vinegar, and olive oil, plus almonds or hazelnuts. Ground in a mortar with a pestle, "a well-made sauce will stick on the calçot," says Vidal. "It can't be too oily."

Shunk

During the festival, which takes place at the height of the European calçot season at the end of January or beginning of February, the shoots are served by the dozen alongside butifarra (pork sausage) and fava beans grilled in their shells. Some restaurants, says Vidal, will highlight calçots from November until April with just a simple menu of grilled meats to supplement them. Traditionally, he adds, those restaurants also force patrons to eat the calçots while wearing a bib, which diners save as a souvenir.

Boqueria brought the festival (sans bibs) to the States four years ago, setting it up in May to correlate with the calçot growing season on this side of the Atlantic, and Vidal, who is from Barcelona and has been eating the calçots since he was a child, drew inspiration from different versions of the onion he's encountered over the years: "When I was studying at culinary school, there was this restaurant outside of Barcelona," he says. "They had a weekend special of calçot, blood sausage, lamb and potatoes al caliu, or wrapped in foil. They were great." He remembers, too, a romesco that a friend's mother used to make: "She would make a grilled calçot and put it in the sauce," he says.

For the Boqueria version, though, he turned to an old family recipe: "My grandmother made romesco with hazelnuts and almonds, so that's how we make it at the restaurant," he says. "And the tomatoes have to be super-roasted."

You can sample the sweet calçots--plus favas, butifarra, and Rosé wine--at the Calçotada festival this Monday from 6:30 to 9 p.m. at Boqueria on 19th Street, where Vidal will set up his grill outside, or on the menu at the Soho location.